Question

What is RMS and peak amplitude?(see attachment)

Answer 1

Peak amplitude is easy - for a signal with a zero average the amplitude is just the maximum value of the signal. The RMS is a little more complicated. It is the root mean square of the signal, or in other words it is the square root of the expected value of the square of the signal,
\[RMS[f(x)]=\sqrt{(b-a)^{-1} \int\limits\limits_{a}^{b}f(x)^{2}dx}\]
For a single sinusoid, say
\[I(t) = A \sin(\omega*t),\]
the RMS turns out to just be A/√2. For the sum of sinusoids, because sinusoids of different frequencies are uncorrelated, the RMS of the sum,
\[I(t)=\sum_{j}^{}A _{j}\sin(\omega _{j}t),\]
is given by,
\[RMS[I(t)]=\sqrt{\sum_{j}^{}A _{j} ^{2}/2},\]
which is the square root of the sum of the variances of each individual component sinusoid. I hope that helps.